1. Field of the Invention
The present invention relates to a face image processing apparatus for extracting information related to nostrils and eyes more accurately from an input face image using a two-dimensional template.
2. Description of the Related Art
As for a conventional face image processing apparatus employing templates of drivers, there is known the apparatus disclosed in Japanese Patent Application Laid-open No. Hei 8-175218 for example. The overall configuration of the conventional apparatus is shown in the form of a block diagram in FIG. 24. This conventional face image processing apparatus includes: a camera 12 for photographing a driver; an image processing unit 13 including an A/D converter, a normalization circuit and a correlation computing circuit; a memory 16 for storing previously therein a standard template and face element arranging data related to eyebrows, eyes and the like; and an electronic control unit (ECU) 14 for discriminating a driving state of a driver on the basis of the processing results from the image processing unit 13 to output a control signal to a warning device 15 to issue a warning.
In addition, the operation, i.e., the flow of the processing, of this apparatus is shown in FIG. 26. In the figure, in Step S101, a face image of a driver is photographed, and for the resultant face image, in Step S102, the variable density normalization is carried out in which the maximum luminance is 256, and the minimum luminance is 1. After having executed the normalization processing, in Step S103, an object template is detected using a standard template. That is, for the image which has been obtained by photographing the face of a driver, a correlation operation is carried out using the standard template which is previously set, and the object template for the driver is produced by a template producing means M2. The operation or function of the template producing means M2 is carried out in a software manner by executing a control program by means of the ECU 14.
The template producing means M2 includes: an object face area setting means M5 for setting an object face area of a driver within an image which has been obtained by photographing the face of a driver; an object eye vicinity area setting means M6 for setting an object eye vicinity area, which is elongated in the vertical direction, of a face containing one eye and one eyebrow within the object face area; and an object eye area setting means M7 for setting an object eye area containing an image of an eye within the object eye vicinity area. The object face area, the object eye vicinity area and the object eye area are made object templates, respectively. After having detected the object templates, the face image of the driver is photographed again and then in Step S104, the variable density normalization is carried out. Then, for the normalized face image, in Step S105, the eye area is detected on the basis of a correlation operation utilizing the object templates. In Step S106, the ECU 14 judges the state of the eyes of the driver on the basis of the image of the eye area the information of which is successively inputted thereto. Then, if it is judged in Step S107 that the eye state of the driver has abnormality, then it is judged that the driver takes a nap, and the warning device is actuated to give a warning against his nap in Step S108.
However, if the image is processed with the image kept as the multi-valued data, then it takes a lot of time to process the data. In addition thereto, the state of the face of a person (e.g., the relation between the eyebrows and the eyes) is changed and unstable due to the accessory information such as wearing or taking-off of glasses, the weather or the hair of the head. In the conventional face image processing apparatus as described above, however, the correlation operation is carried out using the templates having a large amount of information containing eyebrows and eyes. Therefore, it takes much time to retrieve all of the input images and also the retrieval is started using the standard template having no personal information. As a result, there is the possibility that for a face image under the influence of the accessory information that is different from the normal case, the images of the nostrils and the eyes may not be detected in some cases.